Showing papers on "Nitrite published in 1977"
191 citations
TL;DR: During steady state turnover with dithionite and nitrite, the enzyme forms a complex with added nitrite with absorption difference maxima at 445, 538, and 580 nm with respect to reduced enzyme, indicating that nitrite reductase may form complexes with nitrogen compounds of more than one oxidation state.
147 citations
TL;DR: A mechanism is proposed for the suppression of nitrate uptake rate by ammonium through feedback control of the nitrate permease system and/or the Nitrate reductase enzyme system, postulated to be regulated by the level of total amino acids in the cell.
Abstract: The effect of ambient ammonium concentration on the nitrate uptake rate of marine phytoplankton was investigated. These studies consisted of laboratory experiments using unialgal species and field experiments using natural phytoplankton communities. In laboratory experiments, ammonium suppressed the uptake rates of nitrate and nitrite. Approximately 30 min were required for ammonium to exhibit its fully inhibitory effect on nitrate uptake. At high ammonium concentration (>3 μg-at/l), a residual nitrate uptake rate of approximately 0.006 h-1 was observed. When the ambient ammonium concentration was reduced to a value less than 1 μg-at/l, the suppressed nitrate uptake rate subsequently attained a value comparable to that observed before the addition of ammonium. A range of 25 to 60% reduction in the nitrate uptake rate of natural phytoplankton communities was observed at ambient ammonium concentrations of ∼1.0 μg-at/l. A mechanism is proposed for the suppression of nitrate uptake rate by ammonium through feedback control of the nitrate permease system and/or the nitrate reductase enzyme system. The feedback control is postulated to be regulated by the level of total amino acids in the cell.
135 citations
TL;DR: In vivo formation of volatile N-nitrosamines in man after ingestion of a midday meal consisting of a bacon, spinach and tomato sandwich and beer is reported.
Abstract: N-NITROSAMINES, which are thought to be causally related to human cancer1, have been found in μg kg−1 concentrations in polluted air2,3, in water4 and in tobacco products5. Foodstuffs such as cooked bacon, preserved with nitrite, have long been known to contain μg kg−1 amounts of volatile N-nitrosamines formed during cooking6. In vivo formation of N-nitrosamines, after ingestion of suitable amine precursors and nitrite, has been demonstrated in laboratory animals7. In vivo formation in human subjects with hypoacidity, gavaged with relatively massive amounts of diphenylamine plus nitrite, has been demonstrated through detection of N-nitrosodiphenylamine in the stomach contents8. In vivo nitrosation after ingestion of conventional foods has not been demonstrated so far, either in animals or man. We now report in vivo formation of volatile N-nitrosamines in man after ingestion of a midday meal consisting of a bacon, spinach and tomato sandwich and beer.
134 citations
TL;DR: A technique is described by which both oxygen and nitrate (or nitrate or chlorate) levels were continuously monitored during bacterial respiration to suggest that the nitrate reductase is orientated on the plasma membrane so that nitrate gains access from the inner (cytosolic) face.
Abstract: SUMMARY: A technique is described by which both oxygen and nitrate (or nitrite or chlorate) levels were continuously monitored during bacterial respiration. Paracoccus (Micrococcus) denitrificans and Escherichia coli oxidizing succinate rapidly ceased to reduce nitrate when oxygen was available, and equally rapidly commenced nitrate reduction when all the oxygen had been consumed. By contrast, membrane vesicles isolated from P. denitrificans reduced oxygen and nitrate simultaneously. The respiratory nitrate reductase in intact cells of P. denitrificans appeared to be inaccessible to chlorate present in the reaction medium, and it is suggested that the nitrate reductase is orientated on the plasma membrane so that nitrate gains access from the inner (cytosolic) face.
126 citations
TL;DR: In this paper, Nitrogen isotope discrimination during denitrification in soils of nitrate containing natural concentrations of 14N and 15N was studied by determining the amount and the 15N content of Nitrate-N and (nitrate + nitrite)-N in nitrate-treated soils incubated under anaerobic conditions (He atmosphere).
Abstract: Nitrogen isotope discrimination during denitrification in soils of nitrate containing natural concentrations of 14N and 15N was studied by determining the amount and the 15N content of nitrate-N and (nitrate + nitrite)-N in nitrate-treated soils incubated under anaerobic conditions (He atmosphere) for various times after treatment with glucose to promote denitrification. Analyses performed showed that the nitrate-N lost on incubation of these soils could largely be accounted for as products of denitrification (nitrite, NO. N2O and N2). The studies reported show that marked discrimination between 14N and 15N occurs during denitrification of nitrate in soils and that significant N isotope effects occur both in reduction of nitrate to nitrite and in reduction of nitrite to gaseous forms of N. They also indicate that the overall N isotope effect during denitrification of nitrate in soil will depend upon the tendency of the soil to accumulate nitrite under conditions that induce denitrification. It is concluded that discrimination between 14N and 15N during denitrification in soils of nitrate containing natural concentrations of these isotopes is of sufficient magnitude to invalidate the use of N isotope-ratio analyses for assessment of the contributions of soil and fertilizer N to nitrate in surface or ground waters or to nitrous oxide in the atmosphere.
125 citations
TL;DR: Tolerance of coho salmon (Oncorhynchus kisutch) to nitrite was increased when the concentration of chloride ion in the environment was high, thereby interfering with the onset of nitrite-induced methemoglobinemia.
Abstract: Tolerance of coho salmon (Oncorhynchus kisutch) to nitrite was increased when the concentration of chloride ion in the environment was high. The results of flow-through bioassays revealed that no mortality occurred when yearling coho salmon were subjected to nitrite-nitrogen (NO2−–N) of 29.8 mg/l and chloride (Cl−) of 261.3 mg/l for 48 h. When yearling coho salmon were exposed to 3.8 mg/l NO2−–N and 2.5 mg/l Cl− for 12 h, the resultant mortality was 58.3%. Possibly, chloride competes with nitrite for transport across the gills and integumental tissues, thereby interfering with the onset of nitrite-induced methemoglobinemia.
123 citations
TL;DR: Soluble extracts of Methylococcus capsulatus (Bath) that readily oxidise methane to methanol will also oxidise ammonia to nitrite via hydroxylamine, and the kinetics of the oxidation were complex and may involve negative cooperativity.
Abstract: Soluble extracts of Methylococcus capsulatus (Bath) that readily oxidise methane to methanol will also oxidise ammonia to nitrite via hydroxylamine. The ammonia oxidising activity requires O2, NADH and is readily inhibited by methane and specific inhibitors of methane mono-oxygenase activity. Hydroxylamine is oxidised to nitrite via an enzyme system that uses phenazine methosulphate (PMS) as an electron acceptor. The estimated Kmvalue for the ammonia hydroxylase activity was 87 mM but the kinetics of the oxidation were complex and may involve negative cooperativity.
119 citations
TL;DR: The pathway of anaerobic reduction of nitrite to nitrogen gas (N2) by cell suspensions of the denitrifier, Pseudomonas aeruginosa, was studied using the techniques of gas chromatography and mass spectrometry to indicate that nitrite and NO are denitrified by separate pathways, at least prior to the formation of the first bi-nitrogen compound.
103 citations
TL;DR: Nitrite in calcium-free artificial seawater (100 mg NO2- liter-1) was highly toxic but did not induce appreciable methemoglobinemia and adding calcium to this medium decreased the acute toxicity of nitrite.
Abstract: The relative toxicity of nitrite to chinook salmon fingerlings (Oncorhynchus tshawytscha) in both freshwater ([Ca++] = 32 mg liter-1) and natural seawater (32.5‰, [Ca++] = 396 mg liter-1) was measured by 48-h static bioassay. The percentage of hemoglobin oxidized to methemoglobin was also determined. In freshwater, the 48-h median lethal nitrite concentration was 19 mg liter-1. In natural seawater, 1,070 mg liter-1 nitrite caused only 10% mortality in 48 h. In freshwater with 27 mg NO2- liter-1, 44% methemoglobin occurred with 70% mortality. In natural saltwater with 815 mg NO2- liter-1, 74% methemoglobin occurred with 10% mortality. Adding calcium sulfate to the freshwater decreased the toxicity of nitrite but did not reduce methemoglobinemia. Nitrite in calcium-free artificial seawater (100 mg NO2- liter-1) was highly toxic but did not induce appreciable methemoglobinemia. Adding calcium to this medium decreased the acute toxicity of nitrite. These results suggest nitrite toxicity mortalities r...
103 citations
TL;DR: Nitrosamines that cause esophageal cancer in rats were found to inhibit [3H]thymidine incorporation, both in vivo and in vitro, when esophagi were incubated with nitrosamines.
Abstract: Brief reviews are presented on the occurrence of N-nitroso (NNO) compounds, the chemistry and kinetics of NNO compound formation from nitrite and amines or amides, the in vivo formation of these compounds (as detected by tumor induction) on feeding nitrite with amines or amides to rodents, and the carcinogenicity for rats of some new nitrosamides. The possible human hazard caused by exposure to specific readily nitrosated compounds is reviewed. Whether NNO compounds might be causing human cancer of various organs (e.g., pancreatic, nasopharyngeal, and esophageal cancer) is discussed. Some of our results in [3H]thymidine incorporation in the rat esophageal epithelium are presented. Nitrosamines that cause esophageal cancer in rats were found to inhibit [3H]thymidine incorporation, both in vivo and in vitro, when esophagi were incubated with nitrosamines. With reference to the hypothesis that human gastric cancer is caused by nitrosamides (e.g., nitrosoureas), certain correlations were examined between gastric cancer and environmental exposure to nitrate, nitrite, and nitrosatable amides. In studies from our laboratory, dried, salted fish, which was treated with excess nitrite at pH 1 and then "denitrosated" at pH O, yielded 16 mg methylurae/kh fish, possibly derived from methylguanidine.
TL;DR: It is reported here that mutagenesis by two preformed N-nitroso compounds is effectively inhibited by ascorbic acid.
Abstract: MANY chemicals are activated to carcinogens and mutagens by oxidative metabolism to alkylating agents1. Ascorbic acid has been reported to protect against tumour induction in mice by 3-hydroxyanthranilic acid, which induced bladder tumours2 and 7,12-dimethylbenzanthracene plus croton oil which induced skin tumours3. Ascorbic acid can also prevent the formation of carcinogenic N-nitroso compounds from nitrite and amines, in vivo4 and in vitro5. I report here that mutagenesis by two preformed N-nitroso compounds is effectively inhibited by ascorbic acid.
TL;DR: High nitrite levels could depress nitrogen fixation both by inactivation of nitrogenase and by conversion of leghemoglobin into an inactive form by reacting with nitrite present at low concentrations, which is then no longer able to penetrate into bacteroids.
TL;DR: 37 nitrogenous pesticides, belonging to the chemical groups of amides, carbamates and ureas, were nitrosated with sodium nitrite in vitro and no pesticide produced enhanced numbers of micronuclei in mouse bone-marrow erythrocytes when fed together with nitrite.
Abstract: 37 nitrogenous pesticides, belonging to the chemical groups of amides, carbamates and ureas, were nitrosated with sodium nitrite in vitro. The nitrosated compounds were tested for mutagenic activity in the bacterial spot test with Salmonella typhimurium his G 46. Those pesticides reacting positively in this test after nitrosation were then fed to mice in combination with sodium nitrite in order to assess the formation and mutagenicity of these nitroso compounds in vivo. With the already known exception of ethylenethiourea (ETU), no pesticide produced enhanced numbers of micronuclei in mouse bone-marrow erythrocytes when fed together with nitrite. Dose-response experiments with intraperitoneal injection of N-nitroso-ETU revealed an apparent no-effect level of about 15--18 mg/kg. The findings are correlated with the pesticide residues actually present in the environment.
TL;DR: The data suggest that induction of anaerobic NRA in S. lipoferum required nitrate and protein synthesis, and the time course of nitrate reduction was coincidental with the pattern of Nitrate-stimulated N2-ase activity, indicating that a relationship exists between these two processes.
Abstract: Nitrate and nitrite reduction under aerobic, microaerophillic, and anaerobic conditions was demonstrated in Spirillum lipoferum (ATCC 29145). Nitrite did not accumulated during assimilatory nitrate reduction in air. The nitrite produced during dissimilatory nitrate reduction accumulated in the medium but not in the cells. On exposure of the bacteria to nitrate and anaerobiosis, a low initial rate (lag) was followed by accelerated rates of nitrite accumulation. A 3-h anaerobic pretreatment, in the absence of nitrate, did not a void the lag phase. No nitrate reductase activity (NRA) developed in the presence of chloramphenicol. The data suggest that induction of anaerobic NRA in S. lipoferum required nitrate and protein synthesis. Anaerobic N2-ase by S. lipoferum was greatly stimulated in the presence of nitrate. The time course of nitrate reduction was coincidental with the pattern of nitrate-stimulated N2-ase activity inidcating that a relationship exists between these two processes.
TL;DR: Results provide further evidence that ingestion of secondary and tertiary amines together with nitrite can lead to the formation of significant amounts of carcinogenic N-nitroso compounds in the stomach.
01 Jan 1977
TL;DR: In the Peruvian continental shelf and shelf edge at 15S latitude, Nitrate reductase activity was observed at depths ranging between 30 and 250m in 1976 and 1977.
Abstract: In March 1976 and 1977, nitrate reductase, nitrate, nitrite, and oxygen were measured between depths of 30 and 250m in the subsurface waters overlying the Peruvian continental shelf and shelf edge at 15S latitude. Oxygen concentrations of less than 1 ml/l began between 20 and 30 m in both years. The oxygen deficient waters extended to the bottom on the shelf and to 440m at the shelf edge. Nitrate depletion was observed often thoughout the water column in 1976, but it was observed only below 100m in March 1977. Sulfide was occasionally detected below 100m in March 1976, but was not detected at any location in 1977. Nitrate reductase activity was observed at depths ranging between 30 and 250m. The activity between 30 and 50m was likely of phytoplankton origin, while the activity from deeper waters was probably of bacterial origin. The distribution of nitrate reductase activity could not be predicted from the nutrient, oxygen or chlorophyll distribution. In the core of the secondary nitrite maximum between 200 and 250m, nitrate reductase activity ranged from 1.1 to 1.4 ng-at n/h/l in March 1977. A year earlier, at the same location and depth, sulfide was observed. Because of the depth atmore » which this occurred, its association with the secondary nitrite maximum, and the previous occurrence of both nitrate depletion and sulfate reduction, we concluded that this nitrate reductase activity represented bacterial respiration.« less
TL;DR: It appears that another source of nitrite is required, the most likely being the reduction of nitrate to nitrite coupled to the oxidation of organic matter.
Abstract: Growth yields and other parameters characterizing the kinetics of growth of nitrite-oxidizing bacteria are presented. These parameters were measured during laboratory enrichments of soil samples with added nitrite. They were then used to reanalyze data for nitrite oxidizer growth in a previously reported field study (M. G. Volz, L. W. Belser, M. S. Ardakani, and A. D. McLaren, J. Environ. Qual. 4:179-182, 1975), where nitrate, but not nitrite or ammonium, was added. In that report, analysis of the field data indicated that in unsaturated soils, the reduction of nitrate to nitrite may be a significant source of nitrite for the growth of nitrite oxidizers. A yield of 1.23 × 104 cells per μg of N was determined to be most appropriate for application to the field. It was determined that if nitrite came only from mineralized organic nitrogen via ammonium oxidation, 35 to 90% of the organic nitrogen would have had to have been mineralized to produce the growth observed. However, it is estimated that only about 2% of the organic nitrogen could have been mineralized during the growth period. Thus, it appears that another source of nitrite is required, the most likely being the reduction of nitrate to nitrite coupled to the oxidation of organic matter.
TL;DR: The relieving effect of glucose and CO(2) suggests a carrier-mediated nitrate uptake which is more limiting than nitrate reduction and is sensitive to low pH, but which is stabilized by some intermediate originating from an active carbon metabolism.
Abstract: In Ankistrodesmus braunii , in the absence of CO 2 , i.e. in CO 2 -free air or N 2 , photosynthetic nitrate uptake and nitrate reduction were inhibited, especially at low pH. Under such conditions, glucose stimulated nitrate uptake and reduction to almost the same level in the pH range between 6 and 8.5. CO 2 at 0.03% effected an intermediate pH dependence of nitrate uptake; saturating CO 2 concentration (more than 1%) eliminated the pH dependence, as did glucose, but the rates were enhanced compared with glucose. Glucose and, even more, CO 2 , drastically reduced the release of nitrite and ammonia to the medium, the stoichiometry between alkalinization of the medium and nitrate uptake (OH − /NO 3 − ) approached 1. Due to the lack of storage vacuoles in Ankistrodesmus , nitrate uptake and nitrate reduction were closely coupled processes whose experimental separation is difficult. The relieving effect of glucose and CO 2 suggests a carrier-mediated nitrate uptake which is more limiting than nitrate reduction and is sensitive to low pH, but which is stabilized by some intermediate originating from an active carbon metabolism.
TL;DR: Three of the possible explanations of this unusual phenotype are considered: nis-5 creates a new, but inefficient promoter or ‘initiator’, which is not subject to the normal control systems (and therefore causes constitutive, deprepressed synthesis) but whose physical presence reduces maximal enzyme synthesis.
Abstract: The selection of nis-5, a mutation which is tightly linked to the structural genes for nitrate reductase (niaD) and nitrite reductase (niiA) but which only affects nitrite reductase activities, is described. nis-5 single mutants have only 40% of the wild type activity of nitrite reductase after induction by nitrate and, for this reason, grow poorly on nitrate and nitrite. Nitrate reductase activity is not affected, and nis-5 is shown to complement with a niaD- mutation but not with a niiA- mutation.
TL;DR: In this article, the authors used a recirculating sampling device to test the hypothesis that methaemoglobin was formed as the result of the production of nitrite as an intermediate in the rumen.
Abstract: 2. Three experiments with mature dry Friesian cows lasted for up to 16 days. Nitrate was given as nitrate-rich hay or mixed with concentrates to supply from 2.4 to 16.0 g/100 kg liveweight at each meal. To test the hypothesis that methaemoglobin was formed as the result of the production of nitrite as an intermediate in the rumen, one group was given a daily supplement of KNO2, 2 to 3 g/100 kg liveweight. Blood was sampled at frequent intervals, and ruminal fluid was sampled every 15 min for short periods from cows with a recirculating sampling device. Large intakes of nitrate in either form increased nitrite in the rumen, leading to increase of methaemoglobin in the blood during the first few days, after which the high value was maintained. The high methaemoglobin value was positively correlated with the larger nitrite content in the rumen. Results are discussed in the light of conflicting reports on the tolerance of cattle to large amounts of nitrate and the importance of frequent sampling to obtain a true picture is stressed. Previous inferences regarding the ability of cattle to tolerate nitrate at up to 90 g/100 kg are considered to be mistaken.
ADDITIONAL ABSTRACT: In two experiments groups of 4 cows (415-669 kg body weight) received similar daily amounts of NO3- as either a single oral dose of KNO3 (15 g/100 kg) or a single feed of nitrate rich hay (12.4-15.4 g NO3-/100 kg) for 18 days. In a third experiment 6 cows received 2 or 3 g/100 kg of NO3- as a single oral dose of KNO2 for 6 days. Nitrate, nitrite and ammonia were measured in rumen sample and haemoglobin and methaemoglobin were measured in blood. The daily supply of equal doses of nitrate to cows, as hay with a high nitrate content or as potassium nitrate, induced higher nitrite contents in the rumen fluid and a higher percentage of methaemoglobin in the blood during the first days, after which they remained on this higher level. These increases were probably due to a change in the activity of the reducing micro-organisms in the rumen. The changes also partly explain the controversial data in the literature on the acceptable dosages of nitrate to be supplied to ruminants. This may have led to the mis-interpretation that ruminants should tolerate daily intakes up to 90 g of NO3- per 100 g body weight. (Abstract retrieved from CAB Abstracts by CABI’s permission)
TL;DR: The data suggest that the heterotrophic population may be responsible for some of the nitrate produced in these Histosols, after insufficient populations of Nitrosomonas and Nitrobacter were found in a Pahokee muck soil.
Abstract: Insufficient populations of Nitrosomonas and Nitrobacter were found in a Pahokee muck soil (Lithic medidaprit) to account for the nitrate concentration observed. To determine if heterotrophic nitrifiers could account for some of this discrepancy, a method was developed to measure the levels of heterotrophic nitrifiers in soil. A population of 4.1 X 10(5) Arthrobacter per g of dry fallow soil, capable of producing nitrite and/or nitrate from reduced nitrogenous compounds, was observed. Amendment of the much with 0.5% (wt/wt) sodium acetate and 0.1% (wt/wt) ammonium-nitrogen as ammonium sulfate (final concentrations) not only resulted in the usual increase in autotrophic nitrifiers, but also in a fourfold increase in the heterotrophic nitrifying Arrthrobacter. Amendment of like samples with N-Serve [2-chloro-6(trichloromethyl) pyridinel] prevented the increase in Nitrosomonas, but not that in the heterotrophic nitrifiers. Nitrate production in the presence of the inhibitor was diminished but not prevented. An Arthrobacter sp., isolated from the muck, produced nitrite when inoculated at high densities into sterile soil, unamended or amended with sodium acetate and/or ammomium sulfate. These data suggest that the heterotrophic population may be responsible for some of the nitrate produced in these Histosols.
TL;DR: Treatment of certain foods, such as fish, beans and borscht, with 5000 ppm nitrite resulted in the formation of one or more mutagenic principles, as indicated by a Salmonella typhimurium test, which was the most sensitive of several indicator organisms tested.
TL;DR: Evidence is presented which suggests that α-tocopherol affords protection in this animal model for amine-nitrite toxicity by preventing the nitrosative cleavage of aminopyrine to dimethylnitrosamine by sodium nitrite, in the acidic environment of the rat's stomach.
TL;DR: It was found that only OH radicals efficiently attack the substrate, while O2− is necessary for the subsequent formation of nitrite, and determination of the latter reaction allows the detection of the combined presence of both oxygen radical species.
TL;DR: Thiocyanate is a powerful catalyst of nitrosation, which, together with small amounts of nitrite and naturally occurring amines could lead to the intragastric formation of carcinogenic nitrosamines and in certain circumstances be a factor in the aetiology of gastric cancer.
Abstract: The concentrations of nitrite and thiocyanate in fasting and pentagastrin stimulated gastric juice and in saliva have been examined. Nitrite was found in all of 17 samples of fasting gastric juice, mean 4-9 +/- 1-1 muM. Stimulation of gastric secretion with pentagastrin caused no significant change in nitrite concentration. Thiocyanate was detected in all of 21 samples of fasting gastric juice and the difference in concentration between smokers and non-smokers probably reflects similar differences in saliva. In contrast to the nitrite data there was a significant drop in thiocyanate concentration of gastric juice after pentagastrin from 0-9 +/- 0-1 mM to 0-3 +/- 0-04 mM, suggesting a salivary origin for the thiocyanate in gastric juice. Thiocyanate is a powerful catalyst of nitrosation, which, together with small amounts of nitrite and naturally occurring amines could lead to the intragastric formation of carcinogenic nitrosamines and in certain circumstances be a factor in the aetiology of gastric cancer.
TL;DR: It is reported here that nitrosophenols can catalyse N-nitrosamine formation and chlorogenic acid and 4-methylcatechol catalyse the nitrosation of piperidine at gastric pH.
Abstract: THE effect of phenolic compounds on the rate of nitrosation of secondary amines is not a simple one. Tannins inhibit nitrosamine formation1, but in suitable conditions gallic acid catalyses the nitrosation of diethylamine, the rate being dependent on pH and gallic acid concentration2. Some phenolic constituents of smoked foods3 inhibit nitrosation of morpholine at pH 3.0. Phenolic compounds react with nitrite at a much faster rate than do secondary amines4, but chlorogenic acid and 4-methylcatechol catalyse5 the nitrosation of piperidine at gastric pH. We report here that nitrosophenols can catalyse N-nitrosamine formation.